1. Field of the Invention
The present invention relates to image sharpening, and more particularly, to an image sharpening method that utilizes dynamically determined weighting values during an image sharpening process.
2. Description of the Prior Art
Un Sharp Mask (USM) is a technology that allows images to be sharpened. The technology first utilizes a mask, such as a Gaussian mask, to generate a blurred image corresponding to an original image. The blurred image is then subtracted from the original image to obtain a detailed image corresponding to the original image. Finally, the original image is combined with a product of the detailed image and a fixed weighting value to obtain a sharpened image corresponding to the original image. The following equation illustrates the concept of USM.PSHARP=PORIGINAL+α(PORIGINAL−PBLUR),
where α is the fixed weighting value, PORIGINAL is an original pixel value of the original image, PBLUR is a blurred pixel value of the blurred image and corresponds to the original pixel value, (PORIGINAL−PBLUR) represents a detailed pixel value in the detailed image and corresponds to the original pixel value PORIGINAL, and PSHARP is a sharpened pixel value of the sharpened image and corresponds to the original pixel value PORIGINAL.
In the related art, a single weighting value α is utilized to sharpen all the pixels of an original image. If the weighting value α is too small, the sharpened image will be too similar to the original image so that the sharpening result is non-ideal. On the other hand, if the weighting value α is too large, some areas of the sharpened image will be distorted and become too artificial for human perception.